896. Monotonic Array

An array is monotonic if it is either monotone increasing or monotone decreasing.

An array A is monotone increasing if for all i <= j, A[i] <= A[j].  An array A is monotone decreasing if for all i <= j, A[i] >= A[j].

Return true if and only if the given array A is monotonic.

 

Example 1:

Input: [1,2,2,3]
Output: true

Example 2:

Input: [6,5,4,4]
Output: true

Example 3:

Input: [1,3,2]
Output: false

Example 4:

Input: [1,2,4,5]
Output: true

Example 5:

Input: [1,1,1]
Output: true

 

Note:

  1. 1 <= A.length <= 50000
  2. -100000 <= A[i] <= 100000

Rust Solution

struct Solution;

impl Solution {
    fn is_monotonic(a: Vec<i32>) -> bool {
        let mut increasing = true;
        let mut decreasing = true;
        let n = a.len();
        for i in 1..n {
            if a[i] > a[i - 1] {
                decreasing = false;
            }
            if a[i] < a[i - 1] {
                increasing = false;
            }
        }
        increasing || decreasing
    }
}

#[test]
fn test() {
    let a = vec![1, 2, 2, 3];
    assert_eq!(Solution::is_monotonic(a), true);
    let a = vec![6, 5, 4, 4];
    assert_eq!(Solution::is_monotonic(a), true);
    let a = vec![1, 3, 2];
    assert_eq!(Solution::is_monotonic(a), false);
    let a = vec![1, 2, 4, 5];
    assert_eq!(Solution::is_monotonic(a), true);
    let a = vec![1, 1, 1];
    assert_eq!(Solution::is_monotonic(a), true);
}

Having problems with this solution? Click here to submit an issue on github.